Seeking advice from the TT masters. Done the thread searches, so I have some ideas.

2001 TT 225hp Factory Stock

Around town, off the line, up through maybe 3rd she runs like a dream. Pulls good, no CEL, all seems well.

On the freeway it's another story. WOT on the on ramp and the turbo pull is gone at about 50mph. While cruising, throttle down you hear the turbo for a couple seconds then nothing and she feels like a naturally aspirated 1.8.

I haven't found any vac leaks, but still checking (going to try the PVC Pressure test DIY).

I'm not certain if the loss of turbo at higher speed/rpm is the DV or N75, and if so, how to test? as the car works great in the driveway or town speeds??

Help... & Thanks!

 

Boost gauge? Ran a vag?

 

I don't have a boost gauge, but will work to get one.

I have RossTech VAG. Did a full diag and there are currently no codes. I could drive and run VAG to capture data, what measuring blocks do I monitor?

I suspect the boost gauge is going to show boost right as you hit WOT on the freeway, then within seconds boost will drop significantly, maybe entirely.


Might have found my answer on the VAG measuring block (see below). I will give it a try tomorrow.

Channel 115: Requested Boost and Actual Boost

This is a very helpful channel for diagnosing boost leaks, trying to figure out why your car went into limp mode, and seeing if the software or hardware (electronic or manual boost controllers) are doing what they should be. This channel displays the boost requested by the computer (requested boost) in the first column and the boost actually made by the turbo (actual boost) in the second column. The readings you will see here can be misleading. First, you should know that the numbers you will see are not yet corrected for atmospheric pressure (about 1040mbar at sea level). The atmospheric pressure seen at the boost sensor is tough to estimate with complete precision, but I have found that subtracting 1000mbar from the numbers gets you close enough to actual boost unless you are living at 20,000 feet above sea level. The next thing you have probably noticed about these numbers are that they are displayed in mbar instead of psi like we are all used to. Well, this won't be a problem thanks to the metric system. 1000mbar = 1 bar and 1 bar = 14.5psi. There you have it.

 

well its a tiny turbo. KO4 good til about 4500 rpms. The top gear ratios and turbo effeciency arent matched. they mostly comply good fuel economy. I would advise chipping the car, apr or unitronics will offer good power on that turbo frame.

 

I'm not really looking yet to get more out of it, just return to what's missing. The turbo use to spin well at WOT in the highway, now it only does for a second then fades out. Might be a leak, might be N75, might be Bypass, or maybe even the wastegate rod... Don't know.. and not sure yet how to find the culprit.

 

try putting a 6lb spring on the wastegate adjusting nut and the wastegate nipple. this will keep the wastegate closed when it wants to be cracked open when in WOT. this usually only happens with chipped cars though.

you can make a soup can to your turbo inlet pipe then drill a hole at the other end and use a air compressor to check for boost leaks.

on my stock N75 i would see 18 spike down to 13psi. with AEM truboost i see 24psi down to 17psi